The invention relates to a method in reeling of a paper or paperboard web, in which the web is guided by means of a reeling cylinder or a corresponding device guiding the web onto the reel to be formed around a reeling axle, wherein there are at least two reeling axles or the like, both of which are used in turn to reel the web onto the corresponding reel. The invention also relates to a reel-up for a paper or paperboard web.
In the final end of a paper or paperboard machine or in a finishing apparatus such as a coater for paper or paperboard, a continuous fibrous web coming from the preceding sections is reeled around a rotating reeling axle, i.e. a reel spool, to form a reel, i.e. a so-called machine reel. The reeling is conducted by means of a reeling cylinder rotating at the web speed, via which reeling cylinder the web enters the reel. Between the reeling cylinder and the reel, a loading is maintained, which causes a predetermined linear load in a reeling nip located in the contact point of the reel and the reeling cylinder approximately parallel to the reeling axle. Typically, the loading is effected by applying a load to the reel by means of a loading mechanism connected to the ends of the reeling axle towards the stationary reeling cylinder mounted in the frame of the reel-up at the same time when the reeling axle, supported by the ends, moves further apart from the reeling cylinder along with the growth of the reel. The above-described reel-up type is called a Pope-reel. In these reel-ups it is possible to implement the rotating of the reeling axle and the reel with a surface drive, wherein the reeling axle rotates freely in the support structures of the reel-up, and the force required for rotation is transmitted from the reeling cylinder via the reeling nip to the reel, or with a centre-drive, wherein not only the reeling cylinder but also the reeling axle is provided with a drive.
The reel-up type operating with the surface drive is presented e.g. in the Finnish patent 71107 and in the related U.S. Pat. No. 4,634,068. A centre-drive assisted reel-up is disclosed e.g. in the Finnish patent application 905284 by the applicant and in the related U.S. Pat. No. 5,251,835. A centre-drive assisted reel-up which is provided separately with a loading mechanism for the reel and a transfer mechanism for the reel, is disclosed in the European patent 604558 and in the related U.S. Pat. No. 5,393,008.
Because a continuous web is passed from the preceding sections of the paper or paperboard machine or after treatment apparatus of the web at the running speed of the machine or apparatus, a reel change has to be conducted at intervals, i.e. when the reel to be reeled in the reeling station becomes full, the web is cut with a suitable method, which depends e.g. on the grammage of the web, and the new end of the web following the cutting point is guided around a new empty reeling axle, which is brought to the change station from a storage of reeling axles, i.e. from a so-called reel spool storage. The change sequence which is conducted at high web speeds is the most sensitive part of the reeling process, and it involves the transfer of the reeling axle from the reel spool storage to the change position into a change connection with the web travelling onto the reel being completed, the acceleration of the reeling axle to the web speed, cutting of the web in such a way that the web is cut at a desired moment and at a desired point of the reel-up geometry and its guidance immediately around the empty reeling axle, as well as the deceleration and stopping of the full reel of several tonnes in weight after the cutting of the web. There are numerous patents and patent applications related to this change sequence or a part thereof, and as examples reference can be made to the Finnish patent 95683 of the applicant and the related international publication WO 95/34495 (member pressing the web to prevent access of air to the web), to the Finnish application 915432 of the applicant and the related U.S. Pat. No. 5,360,179 (cutting of the web by means of a water jet) and to the Finnish patent 97339 by the applicant and the related EP application publication 739695 (striking blade cutting device for cutting the web with a full-width cut).
The reel spool storage from which the reeling axles are transferred to the change position before initiating the change, is typically located on horizontal rails. The rails are typically located in the travel direction of the web before the reel to be reeled and they end approximately above the reeling cylinder, from which point the first reeling axle is always lowered down to a device for initial reeling by means of lowering arms, as presented e.g. in the U.S. Pat. No. 4,944,467. The U.S. Pat. No. 4,905,925 discloses a reel spool storage in which the reeling axles are placed on rails above the reeling rails supporting the reel in the reeling station, from which position they are lowered downwards along inclined rails to the device for initial reeling in contact with the web travelling on the periphery of the reeling cylinder. The reel spool storage can also be integrated on the reeling rails.
Typically, the reeling cylinder has a stationary position in the frame of the reel-up. However, a solution for a reel-up is also known where the one in which the reeling cylinder is arranged in the frame to move in the vertical direction and to be loaded against the reel, whose position is arranged adjustable on the reeling rails. The solution, which is disclosed in the European patent 697006, enables moving the reeling axles along a straight path from the reel spool storage onto the reeling rails over the reeling cylinder, as well as the fixed position of the reeling axle during the reeling by compensating for the growth of the reel with the downward motion of the reeling cylinder. The European application publication 792829 discloses a reel in which the reeling cylinder to be loaded against the reel is capable of moving in the horizontal direction when the size of the reel grows and the reeling axle is rotating in stationary position.
Consequently, there are numerous known reel-up concepts. A common feature for all the above-mentioned reel-ups is either a stationary reeling cylinder or a moving reeling cylinder and a growing machine reel which is in nip contact therewith and on which reel the web running from the continuous production process or aftertreatment process of paper or paperboard is reeled. In particular, all reel-up concepts share the accurate and demanding change sequence to be effected by means of the reeling cylinder and the empty reeling axle brought in connection with the same. An undisturbed implementation of the change sequence to avoid broke sets high demands on the actuators and automatics, especially at current high web speeds which normally exceed 20 m/s, usually even 25 m/s.
In present centre-drive assisted reel-ups the change is typically implemented in such a way that during the initial reeling when the empty reeling axle has been accelerated to the web speed in the device for initial reeling, the empty reeling axle is in contact with the web travelling via the reeling cylinder, the web travelling via the reeling nip to the reel that is being completed. The reeling nip is opened by moving the reel being completed away from the reeling cylinder and the reeling axle is moved e.g. by means of the device for initial reeling into the change position between the reeling cylinder and the reel being completed, typically in such a way that after the nip between the reeling axle and the reeling cylinder the web travels a short distance on the periphery of the reeling axle and departs therefrom towards the reel. The web is cut after the exit point and guided immediately around the empty reeling axle, and thereafter it is possible to start to decelerate the full reel. The empty reeling axle, around which the web has started to accumulate, is changed when necessary from the device for initial reeling under the load of the loading devices in the reeling station, i.e. to a so-called secondary reeling, and at the same time the centre-drive of the reeling station is connected to the reeling axle. The discontinuity points in the aforementioned change sequence, involving e.g. the act of opening the reeling nip and the stopping of a complete reel at the full reel and the change from the initial reeling to the secondary reeling at the new reel, are, despite of all the technical improvements and precautions, difficult to control and may cause reeling flaws especially in the bottom and surface layers of the reel.
The European patent 483093 discloses, as one alternative, a reel-up in which two reeling cylinders and the corresponding reeling rails are placed on top of each other in such a way that the web can be guided via the upper reeling cylinder to the upper reeling station when the machine reel in the lower reeling station has become full. The path utilized in the change of the web to the upper reeling cylinder is long in the vertical direction, and the reeling cylinders and reeling rails superimposed at the same location in the longitudinal direction of the machine occupy space in the height direction.
The purpose of the invention is to present an improvement for the prior art in continuous reeling-up, and to present a method and a reel-up in which the change sequence in particular can be implemented in a controlled manner, but which also introduces new possibilities for the implementation of the structure of the reel-up and for the production of the reels. To attain this purpose, the method according to the invention is primarily characterized in that the reels are formed in turn in reeling stations located on the opposite sides of a pair of web guiding devices, such as reeling cylinders. When the first reeling cylinder and the corresponding first reeling station are utilized to form a reel, the other one can be free, and if desired, the web can be changed to travel to the other reeling cylinder and onto the reel located in the corresponding second reeling station. A particular advantage of the invention is that the reel that has become full after the reel change as well as the reeling cylinder via which it has been reeled, can be treated in a desired manner without interfering with the new reeling process that has started after the change and is effected by means of the second reeling cylinder. The reels are formed in the machine direction on the opposite sides of the reeling cylinder pairs in their own reeling stations, wherein they can also be moved in different locations of the plane of the machine hall.
The purpose of the invention is also to present a reel-up which provides new possibilities for the implementation of the change sequence of the reel, and new possibilities for the placement of accessory devices. To attain this purpose, the reel-up is primarily characterized in that the reeling stations are placed on the opposite sides of the pair. of web guiding devices, such as reeling cylinders. The reeling cylinders can be placed side by side so that their axes are substantially parallel to each other, wherein their centre axes are on the same height level or on different height levels, wherein their connecting plane can form an angle with the horizontal plane. The invention does not exclude the possibility that the reeling cylinders are placed on top of each other, wherein the aforementioned angle is 90 . In all cases, a passage is formed between the mantle surfaces of the reeling cylinders, via which the web is guided optionally onto either cylinder and the corresponding reel.
As for the other preferred embodiments of the invention, reference is made to the appended dependent claims and to the description hereinbelow.